A model for heat transfer in cryogenic food freezing

Abstract

An experimcntal study of the heat transfer between liquid nitrogen sprays and a model food (a gelatine slab) was carried out under conditions similar to those in a cryogenic freezer. Measurements of heat flux and local mass flow rates of the spray were made at various liquid N2 pressures and various temperature differences between the spray and the food surface.At higher spray pressures, the heat transfer doefficient increases with the mass flux density of the liquid available at the food surface. The quantity of liquid nitrogen sprayed onto the solid surface, the mean droplet size, spray velocity, surface coverage and the mean temperature difference between the boiling nitrogen and the food surface are major factors influencing the rate of heat transfer during the freezing process. Although the heat transfer coefficients at the food surface are much less than those obtained for individual droplets, the model provides useful data.The results are critically discussed in relation to cryogenic freezing of foods.

Evaluation of Green Tea Extract as a Glazing Material for Shrimp Frozen by Cryogenic Freezing

“…The amount of energy removed from the shrimp during the freezing process was 0.84 ± 0.08 kJ s −1 . The short freezing time is attributed to the contact of boiling liquid N 2 directly with the sample, which results in a higher heat transfer rate (Awonorin 1989) and to the lower ambient temperature in the cryogenic freezer. The region T o to T if on the freezing curve corresponds to the sensible heat region during which heat is lost from the product to the medium (Figure 2).…”

Mathematical modeling and simulation of cryogenic tunnel freezers

“…There is very little literature available that discusses the combination of the freezer dynamics with freezing dynamics in the food products (Awonorin, 1989a(Awonorin, , 1989b(Awonorin, , 1997. The mathematical models presented in this section combine the freezing dynamics in the food with the tunnel dynamics for efficient sizing and rating.…”

Extension the Shelf-Life of Fresh Golden Rainbow Trout via Ultra-Fast Air or Cryogenic Carbon Dioxide Super Chilling

“…If the fish is super chilled the temperature equalizes and the water partially frozen out [19]. In the literature were described method for prolongation the shelf life of seer fish (Scomberomorus commersonii) packed in 20% dry ice (solid carbon dioxide) along with 50% water ice and liquid nitrogen spraying [20].…”